It isn't recommended for babies to have a pacifier until after 4 weeks old.
The American Academy of Pediatrics (AAP) recommends delay of the pacifier until breastfeeding is well established at approximately 4 weeks of life.
Some babies have no "nipple confusion" on day 1 and can take a paci without a problem then go right back onto the breast. The average newborn nurses 8-12 times per day, so there is not a whole lot of room for the paci before 4 weeks.
When the frequency of nursing slows down slightly and the time it takes to complete a feed gets shorter, you can introduce a pacifier. There is also a recommendation that young babies be offered the paci as they fall asleep as it may offer some additional protection against SIDS.